This invention relates to diagnostic medical imaging apparatus and more particularly to a mammography machine which employs a near-infrared pulsed laser as a radiation source.
Cancer of the breast is a major cause of death among the American female population. Effective treatment of this disease is most readily accomplished following early detection of malignant tumors. Major efforts are presently underway to provide mass screening of the population for symptoms of breast tumors. Such screening efforts will require sophisticated, automated equipment to reliably accomplish the detection process.
The X-ray absorption density resolution of present photographic X-ray methods is insufficient to provide reliable early detection of malignant breast tumors. Research has indicated that the probability of metastasis increases sharply for breast tumors over 1 cm in size. Tumors of this size rarely produce sufficient contrast in a mammogram to be detectable. To produce detectable contrast in photographic mammogram 2-3 cm dimensions are required. Calcium deposits used for inferential detection of tumors in conventional mammography also appear to be associated with tumors of large size. For these reasons, photographic mammography has been relatively ineffective in the detection of this condition.
Most mammographic apparatus in use today in clinics and hospitals require breast compression techniques which are uncomfortable at best and in many cases painful to the patient. In addition, X-rays constitute ionizing radiation which injects a further risk factor into the use of mammographic techniques as almost universally currently employed.
Ultrasound has also been suggested as in U.S. Pat. No. 4,075,883, which requires that the breast be immersed in a fluid-filled scanning chamber. U.S. Pat. No. 3,973,126 also requires that the breast be immersed in a fluid-filled chamber for an X-ray scanning technique.
It is an object of the present invention to provide an imaging apparatus using light and/or near infrared coupled with ultrafast laser, thus avoiding the drawbacks of prior art X-ray equipment.
It is another object of the present invention to provide a mammography apparatus wherein the patient lies in a prone face down position to the place the woman""s breast in the scanning chamber in such a way as to gather the maximum amount of tissue away from the chest wall, thereby to provide maximum exposed area without breast compression.
It is still another object of the present invention to provide a laser imaging apparatus that uses avalanche photodiode coupled with a low leakage precision integrator for a sensitive detection system.
It is another object of the present invention to provide a laser imaging apparatus with multiplexing technique to allow for efficient gathering of scanned data.
It is yet another object of the present invention to provide a laser imaging apparatus that uses femtosecond pulse width, near infrared laser pulse.
Mammography apparatus of the present invention includes a non-ionizing radiation source in the form of very short pulses of near-infrared wave-length from a solid state laser pumped by a gas laser. The patient lies face down on a horizontal platform with one breast extending through an opening in the platform to hang freely inside a scanning chamber. An optical system converts the laser pulses into a horizontal fanned shaped beam which passes through the breast tissue. The breast is scanned a full 360 degrees starting at that portion of the breast which is closest to the body of the patient and is then stepped vertically downwardly and the scan is repeated at each vertical step until a complete scan of the entire breast has been completed. These light pulses are detected after passing through the breast tissue, converted into electrical signals and then recorded and/or displayed to provide an image of normal and abnormal breast tissues.
These and other objects of the present invention will become apparent from the following detailed description.